Response of the Human Vestibulo-Ocular Reflex System to Constant Angular Acceleration

Abstract

The response of the human vestibulo-ocular reflex system to a constant angular acceleration is calculated using a second order model with an adaptation term. After first reaching a maximum the peracceleratory response declines. When the stimulus duration is long the decay is mainly governed by the adaptation time constant T_a, which enables to reliably estimate this time constant. In the postacceleratory period of constant velocity there is a reversal in response. The magnitude and the time course of the per- and postacceleratory response are calculated for various values of the cupular time constant T₁, the adaptation time constant T_a, and the stimulus duration, thus enabling their influence to be assessed.

Response of the Human Vestibulo-Ocular Reflex System to Constant Angular Acceleration

“…the response of the VOR system to a constant angular acceleration appears to be consistent with the theoretical response, calcu lated in the previous paper [Boumans et al, 1983c]. After reaching a max imum value at about 35 s the peracceleratory response declines.…”

“…Spe cial attention was paid to the peracceleratory response decline, and to the moment of nystagmus reversal in the postacceleratory period. The experi mental data so obtained are reported here and interpreted by means of the previous theoretical study [Boumans et al, 1983c].…”

“…In figure 1 the experimental data for a single test with the stimulus duration of 138 s are fitted, by the least squares method, to equations 4 and 5 of the second order model with adaptation, as outlined in section I of this paper [Boumans et al, 1983c]. This example shows that the cupular T] is 20 s, and Ta is 102 s.…”

“…According to the theoretical calculations [Boumans et al, 1983c;table I], the value of the adaptation time constant Ta could lie between 100 and 150 s, assuming a cupular I-! of 15-20 s. The value of Ta, calculated from the mean values of Aa that are registered at the end of the stimuli of various durations, is found to be 151s.…”

“…the initial rapid decline in peracceleratory response cannot be accounted for by the theoretical model used in the pre vious paper [Boumans et al, 1983c]: it is thus impossible to calculate Ta from the mean values of Aa for stimuli of various durations. The value of Amax2 in this subject is lower than would be expected from the theory.…”